IF it happens again, try booting into the BIOS with only two DIMMs as before, but increase the DRAM voltage by .005 (Or whatever the smallest increment it will allow increases by is) and then save settings, exit BIOS and shut down. Install the other two DIMMs and then power on the system. In fact, it wouldn't be the worst idea to simply do that now.
While that IS a decent quality budget motherboard, it IS a budget entry level board, and doesn't have exceptional memory power phase or VRMs. Ryzen often struggles with four DIMMs installed, so a small increase in DRAM voltage may help to better stabilize it. Also, in the BIOS there may be a setting for the DRAM training voltage (What it is actually called, on that motherboard, might be different, so a little investigation might be required on your part. Often this is called DRAM boot voltage) that is set to something other than what the actual DRAM voltage is set to and you might want to set that DRAM training voltage to the same voltage that you have the actual DRAM voltage set to.
You might also have to experiment with the SOC (Memory controller) voltage as well. As I said, four DIMM configurations are often problematic on Ryzen systems, especially above 2933mhz but at any speed there is potential for problems especially on lower end motherboards. Ryzen also has problems in MANY cases with running four DIMMs unless you up the DRAM voltage, and even then sometimes.